Owing to progress in information communication networks such as Internet in recent years, users can easily access network information through personal terminals employing cellular phones or the like.
In such information communication, information is transmitted as digital signals. Therefore, each user can copy music data and video data, which are transmitted via the information communication network, without degradation in the audio quality and picture quality.
Accordingly, the right of the copyright owner may be significantly infringed when copyrighted content data such as music information and image data are transmitted over the information communication network without appropriate measures for protecting the copyrights.
Conversely, top priority may be given to the copyright protection by disabling or inhibiting distribution of content data over the digital data communication network, which is growing exponentially. However, this causes disadvantages to the copyright owner who can essentially collect a predetermined copyright royalty for copying copyrighted materials.
In the case where the copyrighted content data such as music data is distributed over a digital information network, e.g., configured as described above, each user records the distributed content data on an appropriate recording device, and then reproduces it by a reproducing device.
The recording device for such a purpose may be a medium such as a memory card, which allows electrical writing and erasing of data.
Further, the device for reproducing the content data may be formed of a cellular phone itself, which is used for receiving the content data, or may be a dedicated reproducing device if the recording device is a memory card or the like, and is removably attached to the device receiving the distribution data.
In the above case, security measures are required for the record medium so that the distributed content data cannot be freely transferred from the record medium receiving the data of another record medium or the like without authorization from a copyright owner.
For improving the security of the above system, which is configured to transfer data between devices forming the system and/or through an externally accessible region within the device, it is necessary to give sufficient consideration to authentication processing, encryption processing and others.
As a higher level of security is employed in the authentication processing and encryption processing, an unnecessarily longer time is required even in a regular device before starting the reproduction of the content data for listening or viewing it.